High-temperature synthesis of hexaaluminates by flame spraying pyrolysis

Abstract

The invention relates to a process for preparing aluminates of the general formula (I) A 1 B x Al 12-x O 19-y where A is at least one element from the group consisting of Sr, Ba and La, B is at least one element from the group consisting of Mn, Fe, Co, Ni, Rh, Cu and Zn, x=0.05-1.0, y is a value determined by the oxidation states of the other elements, which comprises the steps (i) provision of one or more solutions or suspensions comprising precursor compounds of the elements A and B and also a precursor compound of aluminum in a solvent, (ii) conversion of the solutions or suspensions or the solutions into an aerosol, (iii) introduction of the aerosol into a directly or indirectly heated pyrolysis zone, (iv) carrying out of the pyrolysis and (v) separation of the resulting particles comprising hexaaluminate of the general formula (I) from the pyrolysis gas.

1 . A process for preparing aluminates of formula (I):
   A 1 B x Al 12-x O 19-y      wherein   A is at least one element from the group consisting of Sr, Ba and La,   B is at least one element from the group consisting of Mn, Fe, Co, Ni, Rh, Cu and Zn,   x=0.05-1.0,   y is a value determined by the oxidation states of the other elements, the process comprising:   (i) providing one or more solutions or suspensions comprising precursor compounds of the elements A and B and also a precursor compound of aluminum in a solvent;   (ii) converting the solutions or suspensions into an aerosol;   (iii) introducing the aerosol into a directly or indirectly heated pyrolysis zone;   (iv) carrying out pyrolysis; and   (v) separating resulting particles comprising aluminate of formula (I) from the pyrolysis gas.   
     
     
         2 . The process according to  claim 1 , wherein the element A is La and the element B is Co or Ni. 
     
     
         3 . The process according to  claim 1 , wherein the element A is Sr or Ba and the element B is Ni. 
     
     
         4 . The process according to  claim 1 , wherein the precursor compound of the element A or B is an acetylacetonate. 
     
     
         5 . The process according to  claim 1 , wherein the precursor compound of the element A or B is a carboxylate. 
     
     
         6 . The process according to  claim 5 , wherein the carboxylate is 2-ethylhexanoate. 
     
     
         7 . The process according to  claim 1 , wherein the precursor compound of the element A or B is an alkoxide. 
     
     
         8 . The process according to  claim 1 , wherein the precursor compound of the element A or B is a nitrate. 
     
     
         9 . The process according to  claim 1 , wherein the precursor compound of the element A or B is an oxide or hydroxide. 
     
     
         10 . The process according to  claim 1 , wherein the precursor compound of aluminum is an alkoxide. 
     
     
         11 . The process according to  claim 7 , wherein the precursor compound of aluminum is aluminum sec-butoxide. 
     
     
         12 . The process according to  claim 1 , wherein the solvent is xylene. 
     
     
         13 . The process according to  claim 1 , wherein the pyrolysis is carried out at a temperature of from 900 to 1500° C. 
     
     
         14 . The process according to  claim 1 , wherein the pyrolysis zone is heated by a flame. 
     
     
         15 - 20 . (canceled)